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OMG! The car really stops with power brakes

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Jim Stabe Avatar
San Diego, CA, USA   USA
For those who don't know I have C4 Corvette suspension and brakes in my car with dual master cylinders and a balance bar (race car stuff). Even with 5/8" master cylinders installed the car's braking still required a heavy leg to get it to stop quickly. I'm getting old and I don't like having to push that hard anymore so I decided to install vacuum boosters. That is vacuum boosters (plural) because I have two separate braking systems for the front and rear brakes and the master cylinders are located inside the passenger compartment behind the dash. When my car had a turbocharged 215 Olds and stock front brakes with Jag XKE rear brakes, I installed a remote booster from an MGC that worked on both the front and rear brakes. The car's stopping power was phenomenal. I scared more passengers with the stopping ability than its acceleration. So I decided to install 2 boosters - one for the front brakes and another for the rears. I found a dual circuit booster setup from a company in the UK that looked like it might be the answer. I wanted to mount it out of the engine compartment but the only place in the car it would fit is on the shelf in the front of the trunk. There were a couple issues putting it there. I didn't want to lose that space in the trunk and the plumbing routing would have been a lot longer. The front brake hydraulic lines would have to go from the master to the trunk and then back again to the front brakes. The vacuum line would have also been longer than I wanted. Besides the plumbing issues the cost of the unit was $400 plus the shipping from the UK. If I ever had a problem with the unit the car would be down for an extended period and I would have to pay shipping both ways.

I finally discovered a single circuit vacuum booster that was only 7" in diameter and was available from a distributor in California. I could buy two of them for $230 (for both) and free shipping. These units were designed for the Australian market and were OEM fitted to several cars. I found a good place to mount the units right under the headlights in front of the front wheel. I had to move bracing members on both sides but it gave me a few advantages. I mounted the front booster on the passenger side and was able to tie into the front brake circuit at the junction of the hard line and flex line to the right front wheel. This means that I only have to penetrate the front of the passenger footwell with one line from the front master cylinder. The rear booster mounts on the drivers side and required 2 penetrations of the front of the drivers footwell, one for the master to booster line and one for the booster output that connects the existing line to the rear brakes. I didn't have to do anything to the existing plumbing aft of the instrument panel. Vacuum runs will be much shorter since both boosters will be right next to the engine. I fabricated a vacuum reservoir out of 1 1/4" thin wall tubing that spans the distance between the two boosters to ensure braking since I have a boosted engine. I installed a one way valve between the engine intake and the reservoir to prevent boost from getting to the reservoir even though the boosters have one way valves built in - belt and suspenders. It took about 17' of brake line to plumb it up but that ia about half of what it would have been if I mounted the boosters in the trunk.

So how does it work? I took it for a drive this afternoon and the feel is exactly how I wanted to be - slightly easier braking at low pedal pressure around town and it will throw you through the windshield if you really stomp the pedal in a panic stop. Full disclosure, I have 275 section tires on the front and 315's on the rear and they are 200 treadwear rated so they are very sticky and wheel lockup takes place at pretty high G force. I want to dial in the front/rear balance and then do some measured stops. I think I can come close to a 100' stop from 60 mph which is what the supercars do with their huge carbon brakes.



Jim

"If you want me to agree with you then we would both be wrong"

'66 MGB widened 11" with supercharged LT1 Chevy and 6 speed, C4 Corvette suspension
Pictures here Part 1 http://forum.britishv8.org/read.php?13,7581
Continued in Part 2 http://forum.britishv8.org/read.php?13,22422
Continued in Part 3 http://forum.britishv8.org/read.php?13,33108
Continued in Part 4 http://forum.britishv8.org/read.php?13,40751
Continued in Part 5 http://forum.britishv8.org/read.php?13,48698,48698#msg-48698
Continued in Part 6 http://forum.britishv8.org/read.php?13,61672

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Drivers side booster installed (1).JPG    38.6 KB
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Passenger side booster installed (1).JPG    45.9 KB
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pinkyponk Avatar
pinkyponk Gold Member Adrian Page
Berwick, NS, Canada   CAN
Wow! That's awesome! Very creative placement.

I'd like to have some power assist on my car some day. Will those units work off the stock MG dual circuit master cylinder?

Adrian



Home built Eaton M62 Supercharger with 7.6psi boost, 8:1 compression, custom "supercharger" cam from Schneider Cams, Mikuni HSR48 Carburetor, Chevy Cavalier 1.6 rocker arms, Maxspeeding rods with Teflon wrist pin buttons, custom aluminum cold air intake, CB Performance computerized ignition, Fidanza 9 pound flywheel, 1.44 exhaust valves in 48cc chamber head, matched manifolds, 2 1/4" exhaust system.

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Jim Stabe Avatar
San Diego, CA, USA   USA
In reply to # 3908891 by pinkyponk Wow! That's awesome! Very creative placement.

I'd like to have some power assist on my car some day. Will those units work off the stock MG dual circuit master cylinder?

Adrian

They should work fine on a dual circuit master. You run the output line from the master to the input of the booster then the output of the booster goes to the brakes. You also need engine vacuum to the booster. The boosters are VH44 units and can be found on EBay. One thing I didn't mention was I installed 3/8" 24 to -3 AN adapters in the boosters so I could plumb the brake lines with 37 degree AN flare hardware.



Jim

"If you want me to agree with you then we would both be wrong"

'66 MGB widened 11" with supercharged LT1 Chevy and 6 speed, C4 Corvette suspension
Pictures here Part 1 http://forum.britishv8.org/read.php?13,7581
Continued in Part 2 http://forum.britishv8.org/read.php?13,22422
Continued in Part 3 http://forum.britishv8.org/read.php?13,33108
Continued in Part 4 http://forum.britishv8.org/read.php?13,40751
Continued in Part 5 http://forum.britishv8.org/read.php?13,48698,48698#msg-48698
Continued in Part 6 http://forum.britishv8.org/read.php?13,61672



Edited 1 time(s). Last edit at 2019-03-14 08:12 PM by Jim Stabe.

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MGB567 Avatar
MGB567 Gold Member Barrie Braxton
Sunshine Coast, Queensland, Australia   AUS
1966 MG MGB MkI "Money Guzzler"
1979 MG MGB GT V8 Conversion "Darkside"
I had a quick look at VH44 but I'm getting "for 4 wheel drum brake" - am I not looking hard enough?



Convertible: CKD 11/66 first registered 8/5/67. Owned since 3/77. 90% original sheet metal. 18GB +40 balanced with almost all new internals. Peter Burgess big valve fast road head. Piper 285. Fidanza FW. Basil's followers and pushrods. TR7clutch. TT exhaust. ARP everywhere. 123 ign. Needham 4synchro c/r box.. Stock rebuilt/replaced suspension. Superpro bushes. New brakes all round including all pipes in SS flex. Interior redone. CAMS approved roll bar and side bars. Lots more. Hybrid of o/e and show/fast road car. Not for sale - it's my toy!

GT: UK car built/sold December '78. Stripped back to bare shell with VW Golf flared guards, flush fit front and rear valances with front guards immovable. Front and rear seams removed,Torana XU1 vents, frenched indicators front & Mk1 rear lights. Powered by 'worked' Rover 5 litre V8 (ex TVR Chimaera) with efi. T5 box. FC IFS. CCE rear attached to Salisbury axle with Quaife. All new interior with MrMikes covers on MX5 seats. Retro4 7x15 rims (zero offset) and 205/55 rubber. Colour: Jaguar Storm. Not for sale - it's my sanity!

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ohlord Avatar
ohlord Gold Member Rob C
North of Seattle, N.W., USA   USA
1957 Land Rover Series I "EYEYIYI"
1971 MG MGB
1971 MG MGB "Bedouin 2"
And nobody insisted an MGB doesn't need better brakes and rear discs are a total waste of time ???
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Stabe and Steer. Dudethumbs up



"I'm a long way gone down this wild road I'm on
It's gonna take me where I'm bound
It's a long way around"



"These are the days that must happen to you"

RD2 Radar/ Electronic Warfare Technician
Vietnam 1969-1972

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Jim Stabe Avatar
San Diego, CA, USA   USA
In reply to # 3908917 by MGB567 I had a quick look at VH44 but I'm getting "for 4 wheel drum brake" - am I not looking hard enough?

This is the same booster kit that I have and it works fine with disc brakes. It may be that one of the particular OEM applications was for a drum brake car but a booster is a booster. It doesn't know what kind of brake it is attached to. All it does is amplify the input pressure using vacuum to output approximately 2X the line pressure going in.



Jim

"If you want me to agree with you then we would both be wrong"

'66 MGB widened 11" with supercharged LT1 Chevy and 6 speed, C4 Corvette suspension
Pictures here Part 1 http://forum.britishv8.org/read.php?13,7581
Continued in Part 2 http://forum.britishv8.org/read.php?13,22422
Continued in Part 3 http://forum.britishv8.org/read.php?13,33108
Continued in Part 4 http://forum.britishv8.org/read.php?13,40751
Continued in Part 5 http://forum.britishv8.org/read.php?13,48698,48698#msg-48698
Continued in Part 6 http://forum.britishv8.org/read.php?13,61672



Edited 1 time(s). Last edit at 2019-03-14 09:43 PM by Jim Stabe.

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